A temperature control device, which controls the temperature of a heating panel on which semiconductor wafers are to be mounted, is disclosed in Patent Literature 1. The heating panel is heated by a heater in this temperature control device, so that the semiconductor wafers mounted on the heating panel are heated. Further, this temperature control device controls the heating operation of the heater so that the temperature of the heating panel becomes a target temperature.
Meanwhile, when a heating panel is affected by a disturbance in the temperature control device disclosed in Patent Literature 1, the temperature of the heating panel exceeds or becomes lower than a target temperature (hereinafter, this target temperature is referred to as an “initial target temperature”). That is, when the heating panel is affected by a disturbance, the temperature of the heating panel is changed.
Here, if the target temperature of the heating panel is temporarily lower than the initial target temperature when the temperature of the heating panel is to exceed the initial target temperature, then the amount of heat applied to the heating panel from the heater is reduced. Accordingly, the excess of the temperature of the heating panel over the initial target temperature is suppressed. Conversely, if the target temperature of the heating panel is temporarily higher than the initial target temperature when the temperature of the heating panel is to become lower than the initial target temperature, the amount of heat applied to the heating panel from the heater is increased. Accordingly, the lowering of the temperature of the heating panel below the initial target temperature is suppressed. Therefore, if the target temperature of the heating panel is made to change contrary to the change of the temperature of the heating panel that will occur if the target temperature of the heating panel is maintained at the initial target temperature when the heating panel is affected by a disturbance, the temperature of the heating panel is maintained at the initial target temperature even though the heating panel is affected by a disturbance.
Meanwhile, in the device disclosed in Patent Literature 1, a disturbance is forcibly applied to the heating panel while the temperature of the heating panel is controlled to the initial target temperature and a temperature change pattern of heating panel at this time is measured. Further, a temperature change pattern, which is contrary to the temperature change pattern of the heating panel at this time, is acquired as a target temperature change pattern of the heating panel when the heating panel is affected by the disturbance. Furthermore, when the heating panel is affected by the same disturbance as the above-mentioned disturbance, the target temperature of the heating panel is changed according to the acquired target temperature change pattern so that the temperature of the heating panel is maintained at the initial target temperature.
As described above, Patent Literature 1 discloses an idea for maintaining the temperature of the heating panel at the initial target temperature by changing the target temperature itself of the heating panel from an initial target temperature according to a target temperature change pattern when the heating panel is affected by a disturbance.